The present invention relates generally to collision judging systems, and more specifically to an improved collision judging system which is particularly suitable for use with, for example, a hood actuating apparatus of a vehicle to protect pedestrians.
Among examples of the conventional collision judging systems is one disclosed in Japanese Patent Laid-Open Publication No. 2001-80545, which is used with a hood actuating apparatus of a vehicle. FIG. 10 hereof schematically shows the disclosed collision judging system, which includes a vehicle speed sensor 101 for detecting a traveling speed of the vehicle 100, at least one acceleration sensor 103 for detecting acceleration produced by an external force acting on a bumper 102 from ahead of the vehicle 100, a deformation rate calculation section 104 for calculating a deformation rate of the bumper 102 on the basis of the acceleration detected by the acceleration sensor 103, and a smoothing section 105. The disclosed collision judging system also includes a vehicle-speed-vs-threshold map 106 for varying a threshold value of the bumper deformation rate in accordance with the detected vehicle speed, a hood actuator 108 for flipping up the hood 109 by a predetermined amount, and a control section 107 for controlling the operation of the hood actuator 108. Once the calculated bumper deformation rate exceeds a predetermined threshold value while the vehicle speed detected by the speed sensor 101 is over a predetermined speed value, the control section 107 determines that the vehicle 100 hits a certain external object (e.g., a pedestrian) M considered to be one of predetermined external objects to be protected from a collision against the vehicle, and then it causes the hood actuator 108 to flip up the hood 109. Thus flipping up the hood 109 via the hood actuator 108 can significantly lessen an impact when the external object M collides against the hood 109.
In such a collision judging system, the acceleration sensor 103 is provided at a front end of the vehicle, while the control section 107, which receives acceleration data and makes a collision judgment, is provided within a vehicle compartment because the control section 107 is in the form of a high-precision electronic control unit (ECU) to be installed in a good operating environment. Therefore, the acceleration sensor 103 has to be connected to the control section 107 via a relatively long signal transmission path; the relatively long signal transmission path would lead to a higher possibility that unwanted electrical noises, such as electromagnetic wave and static electricity, are introduced in the acceleration data transmitted from the acceleration sensor 103 to the control section 107. The electrical noises sometimes prevent the acceleration data from being properly received by the control section 107. As one measure to cope with such electric noises, it has been known to interconnect the acceleration sensor 103 and control section 107 via a serial communication line and use a particular data format, where a check code, such as a parity bit, is inserted before or behind the acceleration data indicative of the sensor-detected acceleration, to permit reliable determination as to whether the acceleration data set has been properly received by the control section 107; this anti-noise measure may more or less contribute to improved communication reliability.
However, with the above-discussed conventional collision judging technique, the acceleration data having been prevented from being properly received by the control section 107 is not used at all in the collision judgment, i.e. no collision judgment is made at all with respect to the acceleration data received improperly during a vehicle collision, and the collision judgment is made only on the basis of subsequent acceleration data properly received by the control section 107. As a consequence, the convention collision judging technique would present very poor collision judging performance. Further, the collision judgment tends to be made intermittently due to the improper reception of the acceleration data, which would also lead to poor collision judging performance
In view of the foregoing prior art problems, it is an object of the present invention to provide an improved collision judging system which achieves enhanced collision judging performance by allowing acceleration data to be successively input to a control section so that the control section can make collision judgment with no unwanted intermission and achieves enhanced collision judging performance.
According to an aspect of the present invention, there is provided a collision judging system which comprises: a sensor unit that includes: an acceleration sensor for detecting acceleration; a data conversion section for converting the acceleration, detected by the acceleration sensor, into an acceleration data set including a check code; and a transmission section for transmitting the acceleration data set converted by the data conversion section; a received data control unit that includes: a reception section for receiving the acceleration data set transmitted from the transmission section of the sensor unit; an error (e.g., data deficiency or shortage) determination section for determining, with reference to the check code included in the acceleration data set, whether or not the acceleration data set has been received properly from the transmission section via the reception section, and outputting the received acceleration data set as a proper data set when it is determined that the acceleration data set has been received properly with no error involved but as an erroneous data set when it is determined that the acceleration data set has not been received properly; and a first storage section for storing a plurality of the acceleration data sets output by the error (data deficiency) determination section; and a collision judgment control unit for making a collision judgment on the basis of a latest proper data set of the plurality of the acceleration data sets stored in the first storage section.
In the collision judging system of the present invention, acceleration values detected successively by the acceleration sensor are each converted into an acceleration data set including a check code, and then the received data control unit determines, on the basis of the check code, whether or not the acceleration data set has been received properly with no error. Each acceleration data set determined as having been received properly is classified as an error-free normal or proper acceleration data set while each acceleration data set determined as not having been received properly is classified as an erroneous acceleration data set, and a predetermined plurality of these classified acceleration data sets are stored in the first storage section. With such arrangements, the present invention can significantly enhance the reliability of data communication between the sensor unit and a controller unit (e.g., an ECU: Electronic Control Unit). Further, because a plurality of the acceleration data sets received in succession are stored in advance for each collision judgment and the collision judgment is made on the basis of the latest proper data set of the stored acceleration data sets, the present invention can make the collision judgment successively with no interruption or intermission.
The collision judgment control unit may include a second storage section for storing the latest proper data set of the plurality of the acceleration data sets stored in the first storage section. When the collision judgment control unit has made an error determination that all of the plurality of the acceleration data sets stored in the first storage section are erroneous data sets, the collision judgment control unit may make the collision judgment on the basis of the proper data set stored in the second storage section. In this embodiment, when the collision judgment control unit has determined, with reference to the received acceleration data sets stored in the first storage section, that all of the acceleration data sets having been received for a predetermined time period up to a current time point are erroneous data sets, it judges that some data deficiencies have occurred in the received data sets, in which case it makes the collision judgment on the on the basis of the proper data set stored in the second storage section. With such arrangements, even when the received data sets have been determined as erroneous data sets in succession, the present invention can make the collision judgment successively with no interruption and can reliably prevent deterioration of the collision judging performance.
The collision judgment control unit may further include a compensating-value calculation section for calculating a predetermined compensating value on the basis of the proper data set stored in the second storage section, a post-determination proper data set input after termination of the error (data deficiency) determination and the number of times the error determination has been made. In this case, when the post-determination proper data set is input immediately after the error determination has been made by the collision judgment control unit at least once, the collision judgment control unit uses, in the collision judgment, a value obtained by adding the compensating value to an acceleration value represented by the post-determination proper data set. Namely, because, in this case, the collision judgment control unit calculates a compensating value on the basis of the proper data set stored in the second storage section, the post-determination proper data set input after termination of the error determination and the number of times the error determination has been made and then makes the collision judgment using the thus-calculated compensating value, it is possible to minimize the deterioration of the collision judging performance.
Preferably, the compensating-value calculation section calculates the compensating value in accordance with a mathematical expression of (Bxe2x88x92A)N/2, where A represents the proper data set stored in the second storage section, B represents the post-determination proper data set, and N represents the number of times the error determination has been made.
Preferably, the collision judgment control unit includes a detected data output section for outputting, as a detected acceleration data set, the latest proper data set of the plurality of the received acceleration data sets stored in the first storage section, a collision-judging-value calculation section for adding respective acceleration values represented by a plurality of the detected acceleration data sets output from the detected data output section and thereby outputting, as a collision judging value, a resultant sum of the acceleration values represented by the detected acceleration data sets, and a comparison section for comparing the collision judging value to a preset collision-judging threshold value. Because, in this case, the acceleration values represented by the detected acceleration data sets output from the detected data output section are added together to calculate the collision judging value and the collision judgment is made by comparing the thus-calculated collision judging value to the preset collision-judging threshold value, the present invention can make the collision judgment with enhanced reliability.
In one embodiment, the second storage section of the collision judgment control unit stores the detected acceleration data set. In this case, when the detected data output section has made an error determination that all of the plurality of the acceleration data sets stored in the first storage section are erroneous data sets, i.e. have data deficiencies, the collision-judging-value calculation section uses, as substitute data, the detected acceleration data set stored in the second storage section to calculate a collision judging value; here, the collision judging value is calculated by adding together the respective acceleration values represented by a plurality of the detected acceleration data sets including the substitute data. With the arrangement that, when it is determined that some data deficiencies have occurred in the acceleration data sets stored in the first storage section, the collision-judging-value calculation section calculates the collision judging value is calculated by adding together the respective acceleration values represented by a plurality of the detected acceleration data sets including the detected acceleration data set stored in the second storage section, the present invention can prevent deterioration of the collision judging performance.
The collision-judging-value calculation section may further include a compensating-value calculation section for calculating a predetermined compensating value on the basis of the detected acceleration data set stored in the second storage section, an post-determination detected acceleration data set input after termination of the error determination and the number of times the error determination has been made. In this case, when the post-determination detected acceleration data set is input immediately after the error determination has been made by the collision judgment control unit at least once, the collision judgment control unit outputs the collision judging value calculated by adding respective acceleration values represented by a plurality of the detected acceleration data sets that include an acceleration value obtained by adding the compensating value to the acceleration value represented by the post-determination detected acceleration data set. By thus using the compensating value when a proper data set has been input after a plurality of data deficiencies occurred in succession, the present invention can prevent deterioration of the collision judging performance with further enhanced reliability.
The compensating-value calculation section may calculate the compensating value in accordance with a mathematical expression of (Bxe2x88x92A)N/2, where A represents the detected acceleration data set stored in the second storage section, B represents the post-determination detected acceleration data set, and N represents the number of times the error determination has been made.
Preferably, the reception section receives an acceleration data set from the transmission section in each predetermined reception cycle, and the detected data output section outputs, as the detected acceleration data set, the latest proper data set of the plurality of the received acceleration data sets stored in the first storage section, in each operating cycle set to an integral multiple of the predetermined reception cycle.
Further, in the collision judging system of the invention, the sensor unit is suitably provided on a deformable member in a front end portion of a vehicle, so as to judge a possibility of a collision with a certain external object at the front of the vehicle. The sensor unit may also be provided in left and right sides of the vehicle.